1. Field of the Invention
This invention generally relates to a combinational weighing or counting apparatus. More specifically, the present invention relates to a combinational weighing or counting apparatus used to weigh with high speed precision articles whose individual weight varies.
2. Background Information
Combinational weighing or counting apparatuses are commonly used to weigh with high speed and precision articles whose individual weight varies, such as sweets or fruits. A combinational weighing or counting apparatus includes, for example, a dispensing feeder shaped like a round table, a plurality of radial feeders (discharge troughs) arranged around the dispensing feeder, and a plurality of weighing hoppers arranged below the radial feeders. The dispensing feeder and the radial feeders can transport articles by electromagnetically induced vibration. The dispensing feeder and the weighing hoppers are each provided with a weighing device (load cell) for measuring the weight of the articles on them.
When a supply device including, for example, a transport conveyor supplies articles to be weighed onto the dispensing feeder, the dispensing feeder transports the articles by vibration in the radial direction while dispensing them in the circumferential direction, and discharges them onto the radial feeders. Then, the radial feeders transport the articles by vibration in the radial direction, and supply them to pooling hoppers. The pooling hoppers temporarily store the articles, and then load them into the weighing hoppers. A combination control means calculates combinations of the weight of the articles loaded into the weighing hoppers from the weight determined by the weighing devices, and selects weighing hoppers, whose combined weight is within the tolerance range. Then, the selected weighing hoppers are opened, and a predetermined amount of the articles is supplied to the devices downstream.
The transported amount of articles supplied to the weighing hoppers from the feeders is adjusted by renewing an operating parameter (vibration time and/or amplitude) of each feeder in accordance with the increase or decrease of the desired weight in the weighing hoppers. As a result, the operating parameters are adjusted such that the weight of the articles in the weighing hoppers approaches the desired weight, and the combined weight approaches the target value.
The supply/stop of the articles to the dispensing feeder from the supply device is determined depending on the weight of the articles accumulated on the dispensing feeder. More specifically, after a predetermined weight of articles has been supplied, the supply device stops supplying articles. The next supply step starts only after the weight of the articles accumulated on the dispensing feeder has dropped below a predetermined minimum weight.
With such a combinational weighing or counting apparatus, the amount of articles supplied to the weighing hoppers from the feeders has to be stabilized in order to increase the weighing precision.
However, in conventional apparatuses, the operating parameters (vibration time and/or amplitude) of the dispensing feeder and the radial feeders are feedback-controlled based on the weight in the weighing hoppers. The amount of articles supplied to the weighing hoppers is determined mainly by the vibration of the radial feeders, but it is also necessary to control the dispensing feeder so as to suitably supply the articles over the entire transport path. Since the control of the operating parameter of the dispensing feeder is based only on the weight in the weighing hoppers, the following problems occur:
Firstly, since the dispensing feeder to be controlled is furthest upstream in the transport path and the weighing hoppers serving as the sensors are furthest downstream, the responsiveness with which the transporting of the articles can be controlled at the dispensing portion is low. Therefore, when the desired amount of articles is not transported into the weighing hoppers, it takes a relatively long time_the apparatus to adjust and transport the desired amount of articles into the weighing hoppers
Secondly, radial feeders, which are controlled separately, are arranged between the dispensing feeder to be controlled and the weighing hoppers serving as the sensors. Thus, optimum control of the dispensing feeder is difficult. That is to say, when the weight in the weighing hoppers varies, it is sometimes difficult to tell whether the reason for this is the dispensing feeder or one of the radial feeders.
In view of the above, there exists a need for a combinational weighing or counting apparatus which overcomes the above mentioned problems in the prior art. This invention addresses this need in the prior art as well as other needs, which will become apparent to those skilled in the art from this disclosure.
It is an object of the present invention to provide a combinatorial weighing or counting apparatus having a dispensing feeder and weighing hoppers, that achieves superior article transport by suitably controlling the operating parameter of the dispensing feeder.
According to a first aspect of the present invention, a combinational weighing or counting apparatus includes a dispensing portion, a plurality of weighing hoppers, a weight detection means, and a control means. Articles to be weighed are supplied to the dispensing portion. From the dispensing portion the articles are supplied to the plurality of weighing hoppers. The weight detection means detects the weight of the articles on the dispensing portion. The control means controls the amount of articles that discharged from the dispensing portion, based on weight information from the weight detection means. With this combinational weighing or counting apparatus, the amount of articles discharged from the dispensing portion is controlled with the weight detection means. The weight detection means is provided for the dispensing portion as a sensor, so that the dispensing portion can be controlled suitably. Thus, superior transport control of the weighed articles is possible with no or only little time lag.
According to a second aspect of the present invention, in a combinational weighing or counting apparatus as in the first aspect, the control means calculates the amount of articles that is discharged from the dispensing portion using the weight information from the weight detection means. The control means controls the amount of articles that is discharged from the dispensing portion, based on this discharge amount. With this combinational weighing or counting apparatus, the amount of articles discharged from the dispensing portion is controlled based on the amount of articles discharged from the dispensing portion. Therefore, the dispensing portion can be controlled suitably, and superior transport control is possible.
According to a third aspect of the present invention, in a combinational weighing or counting apparatus as in the first or second aspect, the control means controls the amount of articles that is discharged from the dispensing portion, based on the weight information while the supply of the articles onto the dispensing portion is stopped. With this combinational weighing or counting apparatus, the weight information is used while the supply of the articles onto the dispensing portion is stopped. Therefore, a precise amount of discharged articles can be obtained. As a result, it becomes possible to control suitably the dispensing portion and superior transport control is possible.
According to a fourth aspect of the present invention, in a combinational weighing or counting apparatus as in any of the first to third aspects, the control means controls the amount of articles that is discharged from the dispensing portion, based on weight information from the weighing hoppers, in addition to the weight information from the weight detection means. With this combinational weighing or counting apparatus, the weight information from the downstream weighing hoppers can be taken into consideration when controlling the discharge amount from the dispensing feeder. Therefore, it is possible to control suitably the amount of articles discharged from the dispensing feeder in accordance with the transport situation of the articles further downstream.
According to a fifth aspect of the present invention, in a combinational weighing or counting apparatus as in any of the first to fourth aspects, the control means controls the amount of articles that is discharged from the dispensing portion, based on weight information from the weight detection means for each weighing cycle. Here, xe2x80x9cweighing cyclexe2x80x9d means not only cycles in the combinational weighing or counting apparatus (loading of articles to be weighedxe2x80x94weighing with the various weighing hoppersxe2x80x94combination calculationxe2x80x94storing of combination weightsxe2x80x94discharge), but also includes the cycles per weighing hopper (loading of articles to be weighedxe2x80x94weighingxe2x80x94sending weight to control meansxe2x80x94combination calculationxe2x80x94discharge). With this combinational weighing or counting apparatus, the dispensing portion is controlled per cycle period, thereby enabling a finely tuned control adapted to the present state.
According to a sixth aspect of the present invention, a combinational weighing or counting apparatus as in any of the first to fifth aspects further includes a supply device supplies articles to the dispensing portion. Further, the control means controls the supply device based on weight information from the weight detection means. With the combinational weighing or counting apparatus of the present invention, the amount supplied from the supply device is controlled in addition to the suitable control of the dispensing portion. Therefore, the transporting of articles in the dispensing portion can be controlled even further.
These and other objects, features, aspects and advantages of the present invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses a preferred embodiment of the present invention.